It is well known that the quantity and quality of physical exercise taken by a person has a significant effect on his/her present and future state of health. A well-known way to reduce the likelihood of heart disease is to stress the heart with suitable exercise/level of strain. The quantity and quality of exercise stimulating the function of the heart can be monitored by a great variety of methods and arrangements. One well known way is to measure the heart rate during the exercise/stress by a heart rate monitor, the readings of which can be examined either in real time or by means of data collected in some data collecting device in no-real time. Research information that can be utilized by the users of heart rate monitors exists about suitable levels of heart rate and the duration of the stresses.
Weight control is also one of the central factors influencing one's health on a general level. If more energy from the food eaten is stored in the tissues of a person than is consumed daily on an average, it inevitably leads to an increase of the weight. Therefore, what is needed is a kind of easy-to-use calorimeter, which measures the energy consumption of a person continuously and easily.
One solution has been presented in the patent publication U.S. Pat. No. 5,749,372. It has made known a set of equipment carried along by a person, by means of which the intensity of the exercise performed by a person can be monitored by means of acceleration measurements. The set of equipment gives the user various acoustic signals, if some predetermined level of exercise has been achieved. The target can be, for example, consuming a certain amount of energy per day. When required, the measurement results of a number of days can be saved in the device, and they can be transferred to an external device through a separate interface. The intensity of the exercise is measured by an acceleration transducer belonging to the device.
Different kinds of exercise stress different parts of the body in different ways. Therefore, by merely monitoring the heart rate it is not possible to get full information on the kind of exercise being performed. A method in which the health effects discovered from measuring the accelerations experienced by the person performing the exercise are utilized, has been presented in the patent application PCT/FI2002/001038. In this application, the effect of the accelerations caused by physical exercise on the development of the bones is described.
A measurement device for the energy consumption caused by physical exercise has been presented in the patent application U.S. Pat. No. 5,989,200. The device includes an acceleration transducer, which measures the movements of the body in one dimension. The type of exercise being performed by the person, the amount of exercise, the force used and the energy consumption of the person are calculated from the acceleration measurements. The measurement device classifies and detects the movements of the body according to a few basic types of exercise. These are sleeping, sitting, standing, walking or running. The energy consumption taking place during each type of exercise has been defined. The detection of the type of exercise is carried out either by using a characteristic describing the exercise, obtained from the acceleration measurements, or a form of acceleration signal describing the exercise. The primary way of detection is the averaging of the peak values of the acceleration maximums for a certain period of time. The decision on the type of exercise is taken on the basis of the calculated average. With the device according to the patent, the detection of the type of exercise can only be carried out on a coarse level. In addition, for detecting the type of exercise, the acceleration signal must also be averaged for a relatively long time. The measuring time must be at least 10s in order to get a result.
The detection of various types of exercise can also be utilized in short-range positioning methods. In them it is attempted to find out how and in which direction the person is moving at any given moment. When the starting point, the form of exercise and duration are known, it can be concluded where the person is at the moment. One possible algorithm has been presented in the journal “International Symposium on Wearable Computers” in its issue of October 2001. The title of the article is “Incremental Motion-Based Location Recognition” and its writers are Seon-Woo Lee and Kenji Mase. In this reference, a method is presented in which the measurement information of two acceleration transducers and a digital angle sensor and/or compass are fed to a decision-making circuit using fuzzy logic. The circuit concludes what the person is doing: Is the person immobile, walking, ascending stairs or descending stairs. It is possible to perform the arrangement presented by an arrangement which in addition to the sensor unit includes one PDA device (Personal Digital Assistant). The PDA device must have a memory of at least 32 Mbit so that the method could be utilized. In addition, the number of different types to be detected is very limited.